The price of a pint of milk is set to rise sharply as soaring feed costs force farmers to switch to cheaper but less efficient feed reducing milk yields and supply.

In a bid to reduce their overheads, some dairy farmers have started buying less high-grain manufactured feed and more forage material such as grass and silage.

This was cheaper, but the animals eating it typically produced less milk, said David Handley, chairman of lobby group Farmers For Action, who estimated that the switch could result in a 2,000 to 3,000 litre fall in yield per cow per year.

"It's like putting ordinary four-star petrol in a Formula 1 car," he said. "But I think you'll find farmers looking at their feed costs very, very carefully and making sure every litre of milk is produced as economically as possible. In some instances, that will mean reducing feed and reducing yield."

Non-aligned dairy farmers whose milk went into cheese manufacturing and who received lower prices than those whose milk was sold as liquid milk were particularly likely to cut back on feed costs, claimed Mansel Raymond, chairman of the National Farmers' Union dairy board.

"I'd say a lot of consultants will be advising farmers to scale back, if possible," he said.

Earlier this month, Dairy Crest Direct, the 1,350-strong group of farmers that supplies Dairy Crest with milk, issued a statement warning: "Either feed prices have to come down significantly (which they show no sign of doing) or milk prices will have to rise significantly, otherwise suppliers will have to cut back feed inputs. This will reduce milk flow and force some out of business."

Spiralling wheat prices have intensified pressure on dairy farmers to reduce feed costs over the past few months. Following last year's poorer-than-expected wheat harvests, they have found themselves spending between £50 and £70 a tonne more on feed than they did last winter [Andersons].